1. Field of the Invention
The present invention relates to a sintered ferrite magnet and a motor provided therewith.
2. Description of the Related Art
As magnetic materials used in a sintered ferrite magnet, Ba ferrite, Sr ferrite, and Ca ferrite having a hexagonal crystal structure are known. Recently, among these magnetic materials, magnetoplumbite type (M type) Sr ferrite has been mainly employed as a magnet material for motors and the like. The M type ferrite is expressed by General Formula of AFe12O19, for example. The Sr ferrite has Sr at an A site of the crystal structure.
As the M type Sr ferrite, Sr ferrite containing a component of Ca and Si has been widely used. Such a Sr ferrite has a tendency that when Ca is increased, squareness ratio (Hk/HcJ) is decreased while residual magnetic flux density (Br) is improved. Such a Sr ferrite also has a tendency that when Si is increased, residual magnetic flux density (Br) is decreased while squareness ratio (Hk/HcJ) is improved. Thus, there is a limit to magnetic characteristics to be obtained.
Therefore, it has been attempted to improve magnetic characteristics. For example, Patent Literature 1 discloses a technique for improving magnetic characteristics by substituting parts of an A-site element and a B-site element with a specific amount of a rare-earth element and Co.
In addition, as a technique for improving magnetic characteristics, in the Sr ferrite, a technique for including Zn and Ti (Patent Literature 2), a technique for including Zn and Mn (Patent Literatures 3 and 4) and the like are proposed.
[Patent Literature 1] JP Patent Application Laid Open No. H11-154604
[Patent Literature 2] JP Patent Application Laid Open No. 2001-052912
[Patent Literature 3] JP Patent Application Laid Open No. H11-251126
[Patent Literature 4] JP Patent Application Laid Open No. 2001-284113